The National Weather Service said temperatures in Boston could be around 100 degrees on Wednesday and Thursday, breaking records for those dates. Meanwhile, cities and towns from the Berkshires to Cape Cod could experience temperatures in the mid-80s to upper 90s.

Weather Service spokesman Bill Simpson said the heat also will come with high levels of humidity, making for a summer blast that will likely hit Massachusetts residents hard.

In preparation, the Massachusetts Emergency Management Agency issued a list of precautions residents should take to avoid heat exhaustion and other health issues. Agency spokesman Scott MacLeod said MEMA encourages people to stay hydrated and avoid strenuous activity. The agency will be on-hand to lend cities and towns help and resources, if needed.

State and local officials also urged residents to stay indoors, in shaded areas, local community "cooling centers" or air-conditioned public buildings.

"In these conditions, we must remember to stay cool and hydrated and keep an eye on our vulnerable neighbors," Mayor Thomas Menino said in a statement.

In Boston, water spray features and air-conditioned community centers will be in operation throughout the day, offering residents opportunities to stay cool. Also, state Department of Conservation and Recreation-run beaches will be staffed with lifeguards, although deep water pools will remain closed until Saturday because of chemical cycles, spokesman S.J. Port said.

Utility companies NSTAR and Western Massachusetts Electric Company said they also were preparing for an increase in electricity use and advising customers to be as energy efficient as possible.